The influence of disturbance on the status and regeneration rate of selected forests in the Udzungwa Mountains, Tanzania

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University of Dar es Salaam
The influence of disturbance by cultivation, fire, and logging on the regeneration of forest cover was assessed in the Udzungwa Scarp Forest Reserve between September 1996 and August 1997. Ten plots were randomly selected in each of four types of forest undisturbed, cultivated, burnt and logged forest. Tree species of at least 1 m height were counted. A questionnaire survey was also conducted for historical information on the nature and extent of disturbances, and the local use of forest resources. The survey revealed that in the past villagers lived in the forest, cultivating food crops and using the forest: resources. Fires were used for the harvesting of honey and hunting, and to widen and maintain the foot paths. The villagers reported that logging developed when the inhabitants surrounding the forest started to build more permanent houses. The effects of disturbance on the vegetation structure were compared with undisturbed forest using Simpson-s Index of Diversity, species dominance, relative and apparent frequencies, and Sorensens Index of Similarity. Quantitative data were also analysed by ANOVA, Canonical Correspondence Analysis (CANOCO), and Steinhaus Index. Disturbance changed the species composition and species richness increasing genetic diversity. The species in all areas belong to many families but in the undisturbed stand the 68 species 32% belonged to the family Rubiaceae. Cultivation reduced the stand to only 183 individuals in 18 species of which only Macaranga kilimandscharica and Trema orientalis were in common with the undisturbed forest. Only 44 species survived under selective logging and mechanical processes including pit sawing. Fire selected against the fire sensitive trees leaving 46 species. Regeneration in the cultivated and fire disturbed sites were largely through invasion, while in the logged area it involves canopy expansion, coppice shoots and regeneration from suckers. Sorensen's index of similarity indicates close structural resemblance between the undisturbed and regenerating logged and burned forest stands. It is suggested that species suitable for regenerating a forest are those species unique to a particular disturbance and those which are abundant in high frequency. However, species with wide adaptation to disturbance, such as Maesa lanceolata and Albizia gummifera should also be considered. For the successful recolonization of cultivated or burned areas the distance to a propagule source and the size of the seed crop is important. The abundant species which the undisturbed forest shared with the disturbed sites would be the most likely source for regeneration propagules.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark (THS EAF SD538.3M67)
Udzungwa, disturbance
Moshi, G.Y (2000) The influence of disturbance on the status and regeneration rate of selected forests in the Udzungwa Mountains, Tanzania, Master dissertation, University of Dar es Salaam. Dar es Salaam.